As a formed cutting tool, in particular, as a cutting tool for forming, for example, the teeth of a gear, a hob comprising a plurality of cutting inserts is known. Such cutting inserts have formed cutting edges. Further, such cutting inserts are removably mounted on a tool body of the hob. In such indexable hob, when a cutting edge is damaged, the relevant cutting insert may be replaced or the direction of the cutting insert may be changed so as to allow another cutting edge to be used. This eliminates the need to replace the entire tool. Such type of cutting insert is economically excellent and the machining can be restarted immediately, and therefore, it has frequently been used, in recent years, in manufacturing sites where productivity is strictly required.
Patent Document 1 discloses an example of such indexable hob. Such hob comprises a plurality of cutting inserts having the same shape. The plurality of cutting inserts is arranged in a helical manner on a peripheral side surface of a tool body having a substantially cylindrical shape. Each cutting insert is arranged such that a helix lead direction thereof and a rake surface thereof intersect with each other in a perpendicular manner.